Azadirachta indica

Journal of Environmental Science and Sustainability (JESS)

Vol.1 (1): 21 – 27, 2013

Comparative Study of Azadirachta indica (Neem) Leaf Powder and Activated Charcoal as an Adsorbent for Removal of Chromium from an Aqueous Solution Divya Majithiya*1, Ajay Yadav 2, Sonal Tawde 3 1-3

Department of Environmental Science, Birla College of Arts, Science & Commerce, Kalyan, Thane, Maharashtra, India *1 [email protected]; [email protected]; [email protected]

Abstract-In the present work, Azadirachta indica (Neem) leaf powder and Activated charcoal have been compared for their adsorptive capacity to remove Chromium (VI) [more toxic than Chromium (III)] from aqueous solution. The equilibrium studies were systematically carried out in a batch process covering various process parameters including agitation time, adsorbent dosage, initial Chromium concentration, volume and pH of aqueous solution. Adsorption behaviour was found to follow the Freundlich’s Adsorption Isotherm in case of both the adsorbents but the Neem powder was proved to be more promising than Charcoal in the removal of Chromium. The adsorption mechanism is described by the pseudo-second order kinetics. Keywords- Adsorption; Neem; Chromium; Charcoal; Kinetics; Isotherm

I. INTRODUCTION Advances in science and technology have brought tremendous progress in many spheres of development, but in the process, also partly contributed to degradation of environment all over the globe due to very little attention paid to the treatment of industrial effluents. Industrial pollution continues to be a potential threat affecting the water. The discharge of non-biodegradable heavy metals into water stream is hazardous because the consumption of polluted water causes various health problems. Waste streams containing heavy metals such as Cu, Zn, Ni, Pb, Cd, and Cr are often encountered in various chemical industries. Among these heavy metals, pollution by chromium is of major concern due to its mutagenic and carcinogenic properties [1]. The metal is used in electroplating, leather tanning, metal finishing, and chromate preparation. Chromium exists in trivalent [Cr (III)] and hexavalent [Cr (VI)] state in aqueous medium. Cr (III) is less toxic and soluble according to Cr (VI) compounds that are both acutely and chronically toxic [2]; however under certain circumstances Cr (III) may be oxidized to Cr (VI) [3]. So removal of chromium, whatever it may be, Cr (III) or Cr (VI), has become important. Little toxic effect is attributed to trivalent chromium when present in very large quantities. Both acute and chronic toxicity of chromium are mainly caused by hexavalent compounds. The most important toxic effects, after contact, inhalation, or ingestion of hexavalent chromium compounds are the following: hepatocellular deficiency, dermatitis, allergic and eczematous skin

reactions, skin and mucous membrane ulcerations, perforation of the nasal septum, allergic asthmatic reactions, bronchial carcinomas, gastro-enteritis, and renal oligoanuric deficiency [4]. The discharge limits from industry is less than 2 mg/L as per most of sthe national & International standard. Chromium is hazardous to health when its limit in potable water exceeds 0.5 mg/L. In industries, removal of chromium is done by using various available techniques, such as precipitation, membrane separation, ion exchange and adsorption. Among these methods, adsorption is most technically and economically feasible and easy method [5]. Commonly used adsorbents like activated carbon, silica, alumina, etc [6][7][8] are expensive, difficult to degrade and may be toxic after certain levels. Thus it has motivated the use of natural material such as biomass, tamarind seeds, and Pomegranate husk, Rice Husk, Fly ash as adsorbents in order to develop cheaper alternatives, which can be disposed off easily in environment without harming it [9][10][11][12]. And so, Azadirachta indica (Neem) leaf powder was tried for the removal of Chromium. II. MATERIALS AND METHODS A. Preparation of Adsorbents 1) Neem: The biomaterial, mature Neem leaves (Azadirachta indica), were collected from the available trees in Birla College, Kalyan area. They were washed thrice with water to remove dust and water soluble impurities and were dried until the leaves became crisp. The leaves were powdered and the resulting neem powder was stored in glass bottle for use as an adsorbent. The presence of niacin, proline, glutamic acid, aspartic acid, glutamine, tyrosine and alanine which contain polar groups like –NH2, -COOH,-OH etc. in neem powder contribute to the negative surface charge; the ingredients contribute an electronegativity of 35.1% [13][14]. 2) Activated Charcoal: Commercially available powdered activated charcoal (PAC) was directly used as an adsorbent.

JOURNAL OF ENVIRONMENTAL SCIENCE AND SUSTAINABILITY (JESS) 1(1): 21 – 27 http://www.jessresearch.com ● ISSN: 2321-5577 - 21 -


B. Experimental Procedure 1000 mg/L of Chromium stock solution was prepared from which a working standard of 300 ppm was prepared. 25 ml of the aqueous solution containing 60 mg/L chromium (VI) was treated with 1 g of adsorbent in 100 ml conical flask for 30 min by shaking on a Rotary Shaker at 160 rpm at Room temperature (28 oC). The sample was allowed to settle and then filtered through a Whatman filter paper No. 1. The filtrate of the sample was analyzed using a Diphenyl carbazide (spectrophotometric) method (APHA, and AWWA-Standard Method for Examination of Water and Waste Water (21st Ed), American Public Health Association Washington D.C) of analysis of chromium for the final concentration of chromium in aqueous solution. The percentage removal of chromium (VI) was calculated as-

Where, Co: Initial Chromium concentration Ct: Chromium concentration at equilibrium after treatment with adsorbent The same experimental procedure was repeated for different agitation times. The agitation time established between the solution and adsorbent was noted. The effects of other parameters such as initial concentrations of chromium in aqueous solution, volume and pH of aqueous solution on % removal of chromium (VI) are obtained at the equilibrium agitation time by following the procedure described above. This procedure is followed for both the adsorbents. The values of the variables studied are as mentioned in Table.1

at a particular point of time, the solution attains equilibrium. The equilibrium agitation time is defined as the time required for the heavy metal concentration to reach a constant value. The equilibrium agitation time is determined by plotting the % removal of chromium against agitation time for a particular adsorbent. Results obtained for effect of agitation time with neem and charcoal as adsorbents are shown in Table 2. TABLE II EFFECT OF AGITATION TIME WITH NEEM AND CHARCOAL

Neem Agitation % Time(min) (tn) Removal 30 86.70 60 90.00 90 93.30 120 96.67 150 98.33 180 100.0 210 100.0 240 100.0 270 100.0 300 100.0 330 100.0 360 100.0

140 Charcoal Neem 120

Adsorbent dosage, m (g/L) Initial Cr concentration in aqueous solution, Co (mg/L) Volume of the aqueous solution, v (ml) pH of aqueous solution

Values investigated for Neem

Values investigated for charcoal

30 - 360

15 – 120

8 - 40

8 – 96

20 - 300

20 – 100

25 -125

25 – 125

3-9

3–9

% Removal

Agitation time, t (min)

Charcoal Agitation % Removal Time(min) (tc) 15 78.33 30 80.00 45 81.67 60 81.67 75 83.33 90 83.33 105 83.33 120 83.33 135 83.33 150 83.33 165 83.33 180 83.33

The % removal of chromium increases upto 180 minutes of agitation time and after that no further increase was recorded for chromium removal by neem leaf powder. The equilibrium agitation time for adsorption of chromium by charcoal was reported as 75 minutes. (Fig.1)

TABLE I EXPERIMENTAL CONDITIONS INVESTIGATED

Parameters

Vol.1 (1): 21 – 27, 2013

Co: 60 ppm v : 25 ml m : 40 g/L

100 80 60

0

50 100 150 200 250 300 350 400 Time (min)

Fig. 1 Effect of equivalent agitation time

B. Effect of Adsorbent Dosage III. RESULTS A. Effect of Agitation Time Kinetic experiments were carried out to evaluate the potential of the adsorbents for the commercial applications. In order to estimate the adsorption capacity of the adsorbent accurately, it is very much important to allow significant time for the experimental solution to attain equilibrium. As the time increases, the amount of solute (here chromium) getting adsorbed by the adsorbent increases, but

The % removal of chromium increased with the increase in adsorbent dosage. In case of Neem, the % removal increased from 36.67% to 100% as the amount of neem powder was increased from 8 gm/L to 40 gm/L. In case of Charcoal, the % removal was increased from 30% to 83.3% with the increase in amount of charcoal from 8 gm/L to 40 gm/L. For getting 100% removal, 96 g/L of Charcoal was required (Fig. 2). Thus, for 100% removal, quantity of neem required was less than that of charcoal.


Vol.1 (1): 21 – 27, 2013


Result obtained for effect of Adsorbent Dosage with neem and charcoal is shown in Table 3.

140

% Removal

120

Co: 60 ppm v : 25 ml

Charcoal Neem

100 80

TABLE IV EFFECT OF INITIAL CONCENTRATION OF CHROMIUM

60

tn : 180 min tc : 75 min

40 20 0

0.5 1 1.5 2 Amount of adsorbent (g)

2.5

Fig. 2 Effect of adsorbent dosage TABLE III EFFECT OF ADSORBENT DOSAGE

Neem Adsorbent % Removal Dosage (gm/L) 8 36.67 16 71.67 24 90.00 32 96.67 40 100.0

Charcoal Adsorbent % Removal Dosage (gm/L) 8 30.00 16 58.33 24 68.33 32 81.67 40 83.33 48 86.70 56 88.33 64 91.67 72 93.33 80 96.67 88 98.33 96 100.0

C. Effect of Initial Concentration of Chromium As the initial concentration of chromium increased, the % removal of chromium decreased.

130 120 110 100 90 80 70 60 50 40 30

Neem Initial Chromium Concentration (mg/L) 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300

% Removal 100.0 100.0 100.0 100.0 100.0 100.0 100.0 99.38 98.33 93.00 89.54 88.33 83.46 82.85 81.67

v :25 ml m :40 g/L


% Removal 90.00 90.00 83.33 77.50 72.00 69.81 63.47 60.18 58.13 52.33 47.69 45.12 42.53 36.00 34.19

As the volume of aqueous chromium solution increased, the % removal of chromium decreased. In case of neem, % removal decreased from 100% to 38.33% with increase in the volume of aqueous solution from 25 ml to 125 ml. Similarly in case of Charcoal also % removal decreased from 83.33% to 30% with increase in the volume of aqueous solution from 25 ml to 125 ml. (Fig. 4)

140

Charcoal Neem

Charcoal Initial Chromium Concentration (mg/L) 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300

D. Effect of Volume of Aqueous Chromium Solution

120

% Removal

% Removal

from 20 mg/L to 300 mg/L. Whereas in case of charcoal, the % removal was decreased from 90% to 72% with the increase in initial chromium concentration from 20 mg/L to 100 mg/L. (Fig. 3) Thus if same quantity of neem and charcoal are taken, then neem is effective for larger range of initial concentration of chromium than charcoal. Results obtained for effect of initial concentration of chromium with neem and charcoal as Adsorbents are shown in Table 4.

Charcoal Neem

Co: 60 ppm v : 40gm/L

100 80


60 40

0 50 100 150 200 250 300 Initial Chromium Concentration (mg/L)

20 20 40 60 80 100 120 140 Volume of Aqueous Solution (ml) Fig. 4 Effect of volume of aqueous chromium solution

Fig. 3 Effect of initial chromium concentration

In case of Neem, the % removal decreased from 100% to 81.67% with the increase in initial chromium concentration

The reason may be attributed to an increase in chromium metal concentration with an increase in volume of the water and the unchanged area of contact of the adsorbent.



Results obtained for effect of Volume of Aqueous Solution with neem and charcoal as Adsorbents are shown in Table 5. TABLE V EFFECT OF VOLUME OF AQUEOUS CHROMIUM SOLUTION

Neem Volume of Aqueous Solution (ml) 25 50 75 100 125

% removal 100.0 81.67 60.00 46.67 38.33

Charcoal Volume of Aqueous % Solution (ml) Removal 25 83.33 50 60.00 75 41.67 100 31.67 125 30.00

E. Effect of pH

% Removal

pH is an important factor controlling the process of adsorption as it affects the surface charge of the adsorbents, the degree of ionization and the species of adsorbate. In case of Neem, the% removal was found to increase from 83.33% to 100% with an increase in pH from 3 to 7. At pH 7 it showed maximum % removal i.e.100%. In contrast to neem, Charcoal showed maximum removal at pH 3. (Fig. 5)

140 Charcoal 130 Neem 120 110 100 90 80 70 tn : 180 min 60 tc : 75 min 50 40 2 4 6 pH

Co: 60 ppm v : 40gm/L

Vol.1 (1): 21 – 27, 2013

TABLE VI EFFECT OF pH

pH 3 4 5 6 7 8 9

Neem % Removal 83.33 91.66 95.00 98.33 100.0 91.66 85.00

pH 3 4 5 6 7 8 9

Charcoal % Removal 98.33 96.67 88.33 83.33 81.67 73.33 48.33

F. Freundlich Adsorption Isotherm Every kind of carbon has its own adsorption isotherm and in the water treatment business this isotherm is definite by the function of Freundlich. The function of Freundlich:

x/m = adsorbed substance per gram active carbon = (Co-Ce)/m Ce = equilibrium adsorbate concentration kf, n = specific constants The above equation can be written as,

The empirical Freundlich relationship does not indicate a finite uptake capacity. This relationship can be reasonably applied to the low or intermediate concentration ranges. The above equation is linearised as

8

10

Fig. 5 Effect of pH

It was confirmed that adsorption increased with the decrease in acidity. At low pH, hydrogen ions compete with chromium ions for appropriate sites on the adsorbent. As pH approaches 7, hydrogen ions become negligible and more chromium ions are bound to the adsorbent. The % removal decreased as pH increased beyond 7. The principal driving force for metal ion adsorption is the electrostatic interaction that is, attraction between adsorbent and adsorbate. The greater the interaction the higher is the adsorption of heavy metal. The neem leaf powder contains 35.1% electronegative components [13][14]. In the present investigation, the maximum % removal of chromium by neem is 100%. The reason can be attributed to the higher electronegativity of the adsorbent, the Neem leaf powder. Results obtained for effect of pH with neem and charcoal as Adsorbents are shown in Table 6.

The present data, when plotted shows good linearity for Freundlich relationship (correlation coefficient, R2=0.9734) in case of neem. The slope of isotherm (n) also satisfies the condition of 0